The Virus Spread Where Restaurants Reopened or Mask Mandates Were Absent

C.D.C. researchers found that coronavirus infections and death rates rose in U.S. counties permitting in-person dining or not requiring masks.

Federal researchers also found that counties opening restaurants for on-premises dining — indoors or outdoors — saw a rise in daily infections about six weeks later, and an increase in Covid-19 death rates about two months later.

“You have decreases in cases and deaths when you wear masks, and you have increases in cases and deaths when you have in-person restaurant dining,” Dr. Rochelle P. Walensky, the director of the C.D.C., said on Friday. “And so we would advocate for policies, certainly while we’re at this plateau of a high number of cases, that would listen to that public health science.”

On Friday night, the National Restaurant Association, which represents one million restaurants and food service outlets, criticized the C.D.C. study as “an ill-informed attack on the industry hardest-hit by the pandemic.” It pointed out that researchers had not controlled for factors other than restaurant dining — such as business closures and other policies — that might have contributed to coronavirus infections and deaths.

“If a positive correlation between ice cream sales and shark attacks is found, that would not mean that ice cream causes shark attacks,” the association said in a statement.

The group also faulted federal researchers for not measuring compliance with safe operating protocols, and it noted that the research did not distinguish between indoor dining or outdoor dining, nor whether restaurants had adhered to distancing recommendations or had adequate ventilation.

“It is irresponsible to pin the spread of Covid-19 on a single industry,” the association said.

“The study is not surprising,” said Joseph Allen, an associate professor at Harvard’s T.H. Chan School of Public Health and director of the university’s Healthy Buildings program. “What’s surprising is that we see some states ignoring all of the evidence and opening up quickly, and removing mask mandates and opening full dining.”

Other researchers said the new study confirmed the idea that viral transmission often takes place through the air, that physical distancing may not be sufficient to halt the spread in some settings, and that masks at least partly block airborne particles.

C.D.C. researchers examined the associations between mask mandates, indoor or outdoor restaurant dining, and coronavirus infections and deaths last year between March 1 and Dec. 31. The agency relied on county-level data from state government websites and measured daily percentage change in coronavirus cases and deaths.

Infections and deaths declined after counties mandated mask use, the agency found. Daily infections rose about six weeks after counties allowed restaurants to open for dining on the premises, and death rates followed two months later.

The report’s authors concluded that mask mandates were linked to statistically significant decreases in coronavirus cases and death rates within 20 days of implementation. On-premises dining at restaurants, indoors or outdoors, was associated with rising case and death rates 41 to 80 days after reopenings.

“State mask mandates and prohibiting on-premises dining at restaurants help limit potential exposure to SARS-CoV-2, reducing community transmission of Covid-19,” the authors wrote.

Shortly after publishing the report, the C.D.C. amended it, urging establishments that resume serving diners to follow agency guidelines for reducing transmission in restaurants.

“The message is, if restaurants are going to open for on-premise dining, it’s important to follow C.D.C. guidelines to do so safely and effectively,” said Gery P. Guy, a scientist with the C.D.C.’s Covid response team and the study’s corresponding author.

That includes “everything from having staff stay home when they show signs of Covid or have tested positive or been in contact with someone who has Covid, and requiring masks among employees as well as customers who are not actively eating or drinking,” Dr. Guy said.

Other steps include adequate ventilation, options to eat outdoors, spacing customers six feet apart, encouraging frequent hand washing, and sanitizing of surfaces that are touched a lot, such as cash registers or pay terminals, door handles and tables.

Even if restaurants limit capacity, however, aerosolized virus may accumulate if ventilation is inadequate, Dr. Allen said.

“It doesn’t really matter if it’s a restaurant, spin class, a gym, a choir practice — if you’re indoors with no masks, low or no ventilation, we know that’s higher risk,” he said. “Respiratory aerosols build up indoors. It’s that simple. This is a real problem for restaurants.”

Linsey Marr, an expert on aerosol transmission at Virginia Tech, said Americans could not be expected to follow all the latest science, and so many simply rely on what is open or closed as an indicator of what is safe.

But indoor dining is particularly risky, she added. People typically sit in a restaurant for an hour or more and don’t wear masks while eating, leaving them vulnerable to airborne virus.

“Limiting capacity will help reduce the risk of transmission, but indoor dining is still a high-risk activity until more people are vaccinated,” she said.

Restaurant workers are particularly exposed. While they can wear masks, diners do not, reducing protection against the virus. And workers spend many hours inside with every shift, Dr. Allen said.

“Now is not the time to let our guard down and pull back on the controls when we’re so close to having a lot of people vaccinated,” Dr. Allen said.

Category: Science

Source: New York Times